TITLE: GCN CIRCULAR NUMBER: 19928 SUBJECT: GRB 160917A: OSN I-band upper limits DATE: 16/09/17 20:49:18 GMT FROM: Zach Cano at U of Iceland A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), Z. Cano (IAA-CSIC) & F. Aceituno (IAA-CSIC) report on behalf of a larger collaboration: We observed the field of GRB 160917A (Racusin et al.; GCN Circ. 19926) with the 1.5-m OSN telescope in Granada, Spain. We began observing at 19:08:34 UT (7.64 hours after the GRB onset), and obtained 14x300s images in I-band. In our coadded image, we find no new source in the refined XRT error circle (Evans et al; GCN Circ. 19927) down to a a 3-sigma limit of I(Vega) = 22.6. The calibration was performed using a nearby star in the USNO B1 catalog, and the upper limit corresponds to an isolated point source in our co-added image.